Tissue pH and Temperature Regulate Pulpal Nociceptors

Blood pH Changes in Dental Pulp of Patients with Pulpitis

The severity of pulpitis is a crucial factor in determining the suitable treatment. There are no clear objective indicators to assess the stage of pulp inflammation that could be used in clinical practice. The change in blood pH of the pulp during the inflammatory phase could hypothetically serve as an indicator of the pulp inflammation severity. The aim of this study was to assess the pH values in the pulpal blood of mature teeth in patients with symptomatic pulpitis, in comparison with the healthy controls. The study included patients with symptoms of pulpitis in premolar or molar teeth (Test group; n = 24, mean age 36.04, SD 7.10), and healthy controls (Control group, n = 6, mean age 24.5, SD 5.94) referred for extraction of premolars or third molars, for orthodontic reasons. The pulpal blood was taken at the opening of the endodontic access cavity, and the pH value was measured in both groups. Statistical analysis was performed using the SPSS 27.0 program with a significance level of p ≤ 0.05. The Mann-Whitney test for dependent samples was performed to evaluate the statistical difference between the groups. The patients with symptomatic pulpitis had significantly decreased pulpal blood pH compared to the healthy controls (p ≤ 0.05). The mean pulpal blood pH was 7.27 (SD 0.06) and 7.40 (SD 0.02) in Test and Control groups, respectively. In the Test group, the pulpal blood pH values were significantly lower in the patients who had symptoms for 3 days or more (7.25, SD 0.05) than in those who had symptoms for up to 3 days (7.33, SD 0.03) (p < 0.001). The pH value of the pulpal blood gradually declines in cases of symptomatic pulpitis, along with increasing duration of the symptoms.

Pulpal anesthesia of maxillary first molars using 4% articaine infiltration in patients with symptomatic irreversible pulpitis: a randomized controlled clinical trial

OBJECTIVES

This study aimed to compare the anesthetic efficacy of 1.8 mL (one cartridge) and 3.6 mL (two cartridges) buccal infiltration and buccal plus palatal infiltration of 4% articaine in maxillary first molar teeth with symptomatic irreversible pulpitis.

MATERIALS AND METHODS

This randomized single-blind clinical trial was conducted on 45 patients with symptomatic irreversible pulpitis of maxillary first molars (Trial Registration No: IRCT2015011020238N2_2015). The patients were randomly divided into three groups (n = 15) for buccal infiltration of 1.8 mL articaine plus 1:100,000 epinephrine (group 1), buccal infiltration of 3.6 mL articaine (group 2), and buccal infiltration of 1.8 mL articaine plus palatal infiltration of 0.5 mL articaine (group 3). The pain intensity was measured by the Heft-Parker visual analog scale (VAS) during injection and during access cavity preparation. No pain or mild pain during treatment was considered as successful anesthesia. Data were analyzed by the Tukey's post hoc test.

RESULTS

The three groups had a significant difference in frequency of the perceived pain during injection (P = 0.01). A higher volume of 4% articaine and injection of articaine in both buccal and palatal sides provided a significantly higher anesthesia success rate (P = 0.049 and P < 0.01, respectively). The highest success rate was recorded in group 3 (93.33%) followed by group 2 (80%) and then group 1 (53.33%).

CONCLUSIONS

Increasing the administered volume of 4% articaine with 1:100,000 epinephrine and addition of palatal infiltration to buccal infiltration of articaine can significantly increase the success of anesthesia in maxillary first molars with symptomatic irreversible pulpitis.

CLINICAL RELEVANCE

Achieving deep anesthesia in teeth with irreversible pulpitis is a critical parameter in management of patients who are in urgent need of root canal treatments.

Do NSAIDs used prior to standard inferior alveolar nerve blocks improve the analgesia of mandibular molars with irreversible pulpitis? An umbrella review

INTRODUCTION

The aim of the present umbrella review was to answer the following question: "Does the use of NSAIDs as premedication increase the efficacy of the standard inferior alveolar nerve block on teeth with symptomatic irreversible pulpitis?"

MATERIAL AND METHODS

Systematic reviews with and without meta-analyses that evaluated the influence of premedication on anesthetic efficacy of the inferior alveolar nerve in symptomatic irreversible pulpitis of mandibular molars were searched in six electronic databases (MEDLINE/PubMed, Scopus, Web of Science, Cochrane Library, EMBASE, and Grey Literature Reports), without the restriction of language or year of publication. A Measurement Tool to Assess systematic Reviews (AMSTAR 2) was used to evaluate the quality of the included studies.

RESULTS

Twelve systematic reviews were included. Only one did not perform a meta-analysis. The AMSTAR 2 overall confidence ranged from very low to high. In general, the main findings of the systematic reviews were that non-steroidal anti-inflammatory drugs (e.g., ibuprofen, oxicam, diclofenac, association of ibuprofen with acetaminophen, and ketorolac) increased the success rate of the inferior alveolar nerve block.

CONCLUSIONS

From the "very low" to "high"-quality evidence available, this umbrella review concluded that NSAIDs as premedication acts through cyclooxygenase pathways and block the synthesis of specific prostaglandins that complicate the mechanism of action of the anesthesia, improving its success rate.

CLINICAL RELEVANCE

Non-steroidal anti-inflammatory drugs can increase the success rate of the anesthetic technique of inferior alveolar nerve block efficacy in situations of mandibular molars with symptomatic irreversible pulpitis.

Effect of preoperative tramadol, ibuprofen, ibuprofen/acetaminophen on the anaesthetic efficacy of inferior alveolar nerve block in patients with symptomatic irreversible pulpitis

The purpose of this double-blind clinical trial was to compare the effect of preoperative tramadol 50 mg, tramadol 100 mg, ibuprofen 600 mg, ibuprofen 600 mg/acetaminophen 1000 mg or placebo 60 min before the administration of inferior alveolar nerve blocks (IANB) of mandibular teeth in patients experiencing symptomatic irreversible pulpitis (SIP). Two hundred and fifty emergency patients diagnosed with SIP were randomly divided into five groups and received medications. Endodontic access was begun 15 min after completion of the IANB, and all patients had profound lip numbness. The Heft-Parker visual analogue scale was used to evaluate pain. Premedication with tramadol 100 mg significantly increased the success rate to 62% than the other groups (p < 0.05). The success rates of ibuprofen, ibuprofen/acetaminophen and tramadol 50 mg groups were not significantly different (p > 0.05). Premedication with tramadol 100 mg enhanced the anaesthetic success of IANB in mandibular molars with SIP.

Comparative evaluation of the effect of two pulpal medicaments on pain and bleeding status of mandibular molars with irreversible pulpitis post-failure of inferior alveolar nerve block: a double-blind, randomized, clinical trial

Background

Complete relief of pain due to irreversible pulpitis is challenging to obtain with analgesic medications. The high incidence of an inferior alveolar nerve block (IANB) failure makes it difficult for practitioners to perform endodontic treatment without implementing other anesthetic techniques, especially mandibular molars. The aim of this study was to compare efficacies of two different quantities of paraformaldehyde based pulpal medicaments to relieve the pain and control hyperemic pulp post-failure of IANB and supplementary technique in patients experiencing this symptomatic irreversible pulpitis in the permanent mandibular tooth.

Method

Eighty-two participants with severe pain pre-operatively (Heft Parker Visual Analogue Scale, VAS > 114 mm) were enrolled, and pain responses were recorded at different time intervals using the Heft Parker visual analogue scale. To the patients experiencing pain even after the administration of the standard IANB and supplemental intraligamentary injection, one of the two paraformaldehyde based pulpal medicaments was placed in the pulp chamber and sealed. Participants were recalled after 24-48 h (second visit) to assess pain and bleeding reduction.

Results

Results showed a significant decrease in pain severity and bleeding score post medicament placement (p < .05). Hence judicious use within a recommended period, pulpal medicaments can be considered safe.

Conclusion

Paraformaldehyde based pulpal medicament can be used as an alternative to manage pain in patients having severe irreversible pulpitis and hyperalgesia.

Anaesthetic Efficacy of Lidocaine and Articaine in Inferior Alveolar Nerve Block Combined with Buccal Infiltration in Patients with Irreversible Pulpitis

Purpose:

This prospective, randomized, double-blinded study was conducted to compare the anesthetic efficacy of 2% lidocaine with 1:200,000 epinephrine and 4% articaine with 1:200,000 epinephrine in inferior alveolar nerve block (IANB) combined with buccal infiltration in patients with irreversible pulpitis.

Methods:

Group I: Thirty patients received IANB of 2% lidocaine without buccal infiltration. Group II: Thirty patients received IANB of 2% lidocaine followed by buccal infiltration with 2% lidocaine. Group III: Thirty patients received IANB with 4% articaine followed by buccal infiltration with 4% articaine. Pain during the procedures was recorded by using a Heft Parker visual analog scale. No pain or mild pain on endodontic access was recorded as success and analyzed using Chi-square analysis.

Results:

Group I obtained 30% success rate. Fifty percent successful anesthesia was obtained for Group II. The success rate was increased to 70% for Group III with statistically significant difference among all the groups (P < 0.05).

Conclusion:

The use of 4% articaine as both IANB and buccal infiltration recorded the highest success rate (70%) when compared to either 2% lidocaine as IANB with buccal infiltration (50%) or 2% lidocaine as IANB alone (30%) in patients with irreversible pulpitis.

[Preventive analgesia for the improvement of local anesthesia efficacy in treatment of acute pulpitis in molars]

THE AIM OF THE STUDY

Was the assessment of the efficacy of using non-steroidal anti-inflammatory drug Ketorol Express as a preventive analgesia in the treatment of acute pulpitis in molars.

MATERIALS AND METHODS

The study comprised 128 individuals, 76 (59.4%) women and 52 (40.6%) men. The mean age was 37.4 years. Two different visual-analog scales were used to evaluate the effectiveness of pain relief and the general well-being of the patient and the doctor.

THE RESULTS

Of the study proved that the preventive analgesia with Ketorol Express at a dosage of 20 mg 15 minutes before local anesthesia with 4% articaine with epinephrine 1:200 000 in patients diagnosed with acute pulpitis of molars was effective since local anesthesia high effectiveness, absence of necessity for alternate anesthesia were registered by patients, which coincided with the dentist's opinion.

CONCLUSION

Preventive analgesia with Ketorol Express improves the efficacy of local anesthesia in the treatment of acute pulpitis in molars.

Comparing the Efficacy of Twin Mix and Lidocaine for Inferior Alveolar Nerve Blocks in Patients With Symptomatic Irreversible Pulpitis

This randomized, active-controlled, double-blind, prospective clinical trial evaluated the anesthetic efficacy of 2% lidocaine with 1:200,000 epinephrine versus an admixture of 2% lidocaine with 1:200,000 epinephrine and 1 mL of 4 mg dexamethasone (Twin mix) for inferior alveolar nerve blocks (IANBs) in patients with symptomatic irreversible pulpitis (SIP) of the mandibular molars. Seventy-eight patients with SIP of mandibular molars were randomly allocated to the 2 groups of 39 subjects. All patients were required to have profound lip numbness within 10 minutes of local anesthetic deposition. The efficacy of pulpal anesthesia was confirmed by absence of pain or mild pain (Heft-Parker visual analogue scale ≤54 mm) during access cavity preparation and placement of glide path files. The collected data were subjected to independent t test, chi-square test, and Fisher exact test using SPSS software version 20.0 at a significance level of 0.05. IANB success rates for the lidocaine group and the Twin mix group was 66% and 68% respectively, which was not a statistically significant difference (p > .05). This study demonstrated that the anesthetic efficacy of Twin mix was equivalent to 2% lidocaine for IANBs in teeth with SIP.

Preoperative Intraligamentary Injection of Dexamethasone Can Improve the Anesthetic Success Rate of 2% Lidocaine during the Endodontic Management of Mandibular Molars with Symptomatic Irreversible Pulpitis

INTRODUCTION

The aim of this randomized, double-blind clinical trial was to evaluate the effect of preoperative administration of intraligamentary injections of diclofenac sodium and dexamethasone on the anesthetic efficacy of 2% lidocaine given as an inferior alveolar nerve block in the endodontic management of symptomatic irreversible pulpitis.

METHODS

One hundred seventeen patients randomly received 1 of the 3 intraligamentary injections before the endodontic treatment: 0.9% normal saline, 25 mg/mL diclofenac sodium, or 4 mg/mL dexamethasone. After 30 minutes, patients received an inferior alveolar nerve block with 2% lidocaine and 1:80,000 epinephrine. The teeth were tested with electric pulp testing after 10 minutes. In case of a positive response, the anesthesia was considered as "failed." If the electric test response was negative, a rubber dam was applied, and endodontic treatment was started. Any pain during the treatment was recorded. The anesthesia was considered successful if the patients experienced no pain or faint/weak/mild pain during root canal access preparation and instrumentation (Heft-Parker visual analog scale score <55 mm). The effect of intraligamentary injections on maximum heart rates was also recorded. The anesthetic success rates were analyzed with the Pearson chi-square test at 5% significance.

RESULTS

The control, diclofenac sodium, and dexamethasone groups had anesthetic success rates of 32%, 37%, and 73%, respectively. Dexamethasone was significantly more successful than the control and diclofenac sodium groups (P < .001, χ²₂ = 14.7). There were no differences between the control and diclofenac groups (P > .05). All the solutions did not significantly affect heart rates.

CONCLUSIONS

The administration of an intraligamentary injection of dexamethasone before endodontic intervention of mandibular molars with symptomatic irreversible pulpitis increases the success rates of an inferior alveolar nerve block with 2% lidocaine.

Alternative techniques for failure of conventional inferior alveolar nerve block

Successful local anesthesia in dental treatment is the most important prerequisite for pain control of patients. However, unlike that in the maxilla, it is difficult to administer local anesthesia in the mandible, and the success rate of conventional inferior alveolar nerve block (IANB) is only 80–85%. It is attributed to various causes such as anatomical variations, extreme anxiety, and technical errors; thus, various alternatives have been devised to improve this. We will analyze the causes of failure in conventional IANB and examine various alternatives that can be applied in these cases.

Efficacy of Endo-Ice followed by intrapulpal ice application as an adjunct to inferior alveolar nerve block in patients with symptomatic irreversible pulpitis-a randomized controlled trial

OBJECTIVE

The purpose of the present study was to evaluate the effect of Endo-Ice followed by intrapulpal ice application for reducing pain during pulp extirpation in mandibular molars with symptomatic irreversible pulpitis.

MATERIALS AND METHODS

Sixty patients diagnosed with symptomatic irreversible pulpitis participated in the present study. Subjects were randomly allocated to any one of the following groups: control group-inferior alveolar nerve block with lignocaine (2%) adrenaline (1:80000), articaine group-inferior alveolar nerve block with lignocaine (2%) adrenaline (1:80000) + Buccal infiltration with articaine (4%) with adrenaline (1:100000); or cold group-inferior alveolar nerve block with lignocaine (2%) adrenaline (1:80000) + cold application. The outcome assessor measured the level of pain during access opening and pulp extirpation using the visual analogue scale. The anxiety level of the patient was also measured.

RESULTS

During access opening, there was a significant difference in the pain reduction in the articaine group when compared to cold and control group (p value = 0.02). During pulp extirpation, cold group and articaine group showed a significant reduction in pain levels as compared to the control group (p value = 0.001). There was no difference in the pain level during pulp extirpation among the two test arms (articaine and cold) (p value = 0.99). Further, cold significantly reduced the level of anxiety when compared to the articaine or control group (p value = 0.001).

CONCLUSION

Hence, cold is a simple, supplementary technique in reducing pain during pulp extirpation.

CLINICAL RELEVANCE

Application of cold may help in minimizing the fear of additional injection in managing pain during endodontic treatment.

Effect of ibuprofen on the efficacy of inferior alveolar nerve block in patients with irreversible pulpitis: A meta-analysis

The aim of this study was to compare preventive ibuprofen administration to placebo on the efficacy of inferior alveolar nerve block in patients with irreversible pulpitis. A search was performed in PubMed, Scopus, Web of Science, LILACS, BBO, Cochrane Library, SIGLE, and grey literature. The risk of bias was evaluated through the Cochrane Collaboration's tool. The quality of evidence was assessed using the GRADE approach. Only seven studies remained for the meta-analysis. Administering ibuprofen before anaesthesia increased the success rate of injectable anaesthesia (RR = 1.79; 95% confidence interval (CI) 1.32-2.42; P = 0.0002) even in cases of symptomatic irreversible pulpitis (RR = 1.55; 95% CI 1.05-2.29; P = 0.03). The intensity of pain was lower for ibuprofen (standardised difference means (SMD) = -3.73; 95% CI -6.43 to -1.04; P = 0.007). Ibuprofen as premedication is beneficial for the success of inferior alveolar nerve block.

Anesthetic Efficacy of Gow-Gates Nerve Block, Inferior Alveolar Nerve Block, and Their Combination in Mandibular Molars with Symptomatic Irreversible Pulpitis: A Prospective, Randomized Clinical Trial

INTRODUCTION

The purpose of this prospective, randomized clinical trial was to evaluate the anesthetic efficacy of the Gow-Gates nerve block (GGNB), the inferior alveolar nerve block (IANB), and their combination for mandibular molars in patients with symptomatic irreversible pulpitis.

METHODS

One hundred fifty patients diagnosed with symptomatic irreversible pulpitis of a mandibular molar were selected. The patients randomly received 2 GGNB injections, 2 IANB injections, or 1 GGNB injection plus 1 IANB injection of 1.8 mL 2% lidocaine with 1:80,000 epinephrine. Access cavity preparation was initiated 15 minutes after injections. Lip numbness was a requisite for all of the patients. Success was specified as no or mild pain on the basis of Heft-Parker visual analog scale recordings during access cavity preparation or initial instrumentation. Data were analyzed with the chi-square, Kruskal-Wallis, and analysis of variance tests.

RESULTS

The success rates of anesthesia were 40%, 44%, and 70% for the GGNB, IANB, and GGNB + IANB groups, respectively. There was no statistically significant difference in the success rate of anesthesia between the GGNB and IANB groups (P > .05). The anesthesia success rate for the GGNB + IANB group was significantly different from those of the GGNB and IANB groups (P < .05).

CONCLUSIONS

A combination of GGNB and IANB could improve the efficacy of anesthesia in mandibular molars with symptomatic irreversible pulpitis, but it would still require supplemental anesthesia. Further research may be needed to confirm the results of this study.

Capsaicin-sensitive Innervation Modulates the Development of Apical Periodontitis

INTRODUCTION

Nociceptive neurons play a critical role in the detection of stimuli evoking actual or potential tissue injury. In addition, they are involved in neurogenic inflammation by the peripheral release of neuropeptides such as calcitonin gene-related peptide (CGRP). The dental pulp and periradicular tissues are innervated by capsaicin-sensitive neurons known to release CGRP. However, the role of these capsaicin-sensitive neurons in the development of apical periodontitis is largely unknown. The aim of this study was to evaluate the contribution of peptidergic neurons to the development of apical periodontitis.

METHODS

Neonatal Sprague-Dawley rats were injected with vehicle (control group) or a single subcutaneous capsaicin dose to cause the selective ablation of peptidergic neurons (neonatal capsaicin group). Ablation of capsaicin-sensitive neurons was verified with confocal microscopy, capsaicin-induced eye-wipe nocifensive behavior test, and by measurement of immunoreactive CGRP levels in the dental pulp. Five weeks after ablation, standardized pulp exposures were made in the mandibular left first molars. Mandibles were harvested at 7, 14, 21, and 28 days after pulp exposure and imaged with micro-computed tomography (μCT) to quantify apical lesion volume. Data were analyzed by using 2-way ANOVA analysis with Bonferroni post hoc test.

RESULTS

Rats in the control group displayed a robust capsaicin-induced nocifensive behavior, which was nearly abolished in the neonatal capsaicin group. In addition, the neonatal capsaicin group showed a significant depletion of susceptible neurons and CGRP in the dental pulp compared with control. Importantly, micro-computed tomography analysis showed larger periradicular lesions at 7 and 14 days after pulp exposure in the neonatal capsaicin group when compared with control.

CONCLUSIONS

Results identify a protective role for capsaicin-sensitive neurons in the initial phase of apical periodontitis. Thus, interventions or disorders that alter activity of capsaicin-sensitive fibers are likely to alter the development of apical periodontitis.

Effects of Extracellular pH on Dental Pulp Cells In Vitro

INTRODUCTION

The proliferation and migration of dental pulp stem cells (DPSCs), a population comprised of dental pulp cells (DPCs), are important processes for pulp tissue repair. Dental pulp is exposed to changes in extracellular pH under various conditions, such as acidosis and exposure to caries-associated bacteria or a pulp capping agent. The objective of this study was to investigate the effects of extracellular pH on DPC proliferation and migration in vitro.

METHODS

To evaluate the proliferation potency of DPCs in various extracellular pH conditions, 2 × 10(4) cells were seeded into 35-mm dishes. The following day, we changed to NaHCO3-free medium, which was adjusted to different extracellular pH levels.

RESULTS

After 120 hours, DPCs cultured in media from a pH of 3.5 to 5.5 showed cell death, those cultured in conditions from a pH of 6.5 to 7.5 showed growth arrest or cell death, and those grown at a pH of 9.5 showed mild proliferation. The migratory activity of living DPCs was not affected by extracellular pH. For histologic analysis, human teeth possessing a small abscess in the coronal pulp chamber were sliced for histologic analysis. Proliferating cell nuclear antigen (PCNA) immunolocalization was used as an index of cell proliferation for the sections and cultured cells. Acidic extracellular pH conditions resulted in reduced numbers of PCNA-positive DPCs in the dishes. As for pulp tissue affected by a small abscess, a PCNA-negative pulp cell layer was observed in close proximity to the infectious lesion.

CONCLUSIONS

Together, these results suggest that an acidic extracellular pH condition is associated with DPC growth arrest or cell death.

The efficacy of pre-operative oral medication of paracetamol, ibuprofen, and aceclofenac on the success of maxillary infiltration anesthesia in patients with irreversible pulpitis: A double-blind, randomized controlled clinical trial

AIM

To determine the effect of preoperative administration of paracetamol (PARA), ibuprofen (IBUP), or aceclofenac (ACEC) on the success of maxillary infiltration anesthesia in patients with irreversible pulpitis in a double-blinded randomized controlled trial.

MATERIALS AND METHODS

One hundred and twenty patients with irreversible pulpitis of a maxillary first molar participated. Patients indicated their pain scores on a Heft Parker visual analog scale, after which they were randomly divided into four groups (n = 30). The subjects received identical capsules containing 1000 mg PARA, 800 mg IBUP, 100 mg ACEC or cellulose powder (placebo, PLAC), 1 h before administration of maxillary infiltration anesthesia with 2% lidocaine containing 1:200,000 epinephrine. Access cavities were then prepared and success of anesthesia was defined as the absence of pain during access preparation and root canal instrumentation. The data were analyzed using chi-squared tests.

RESULTS

The success rates in descending order were 93.3% (IBUP), 90% (ACEC), 73.3% (PARA), and 26.5 % (PLAC). A significant (P < 0.001) difference was found between the drug groups and the PLAC group.

CONCLUSIONS

Pre-operative administration of PARA, IBUP, and ACEC significantly improved the efficacy of maxillary infiltration anesthesia in patients with irreversible pulpitis.

Impacted lower third molars: Can preoperative salivary pH influence postoperative pain?

Aim

The literature focuses little attention on factors that influence third molar post extraction pain (PEP). One factor that may play a role in PEP is saliva. We undertook a study in patients subjected to third molar extraction with the aim of assessing the influence of salivary pH on PEP.

Materials and Methods:

Thirty-one healthy patients with one impacted inferior lower third molar with mean age of 21.02 ± 2.05 years, underwent surgery for similar impactions. The process of pH measuring was carried out without delay after saliva collection, with a combination electrode connected to a PHM 62 pH meter. Pain assessment was done at 4, 8, 12, 18 and 24 hours on the first day. The scale ranged from 0 to 10 in which 0 and 10 denoted ‘no pain’ and ‘maximum pain,’ respectively.

Results:

The multivariate analysis suggests that the factors that influence pain are patients’ sex (B = - 0.466) and the saliva pH (B = - 1.093). According to the findings of our study, PEP intensity is assumed to have a reverse correlation with salivary pH and is also assumed to be greater in females.

Conclusion:

Due to the fact that no previous study has indicated such findings so far, further studies are needed to assess the importance of preoperative pH value and its clinical significance on the level of PEP.

Comparative evaluation of anesthetic efficacy of Gow-Gates mandibular conduction anesthesia, Vazirani-Akinosi technique, buccal-plus-lingual infiltrations, and conventional inferior alveolar nerve anesthesia in patients with irreversible pulpitis

OBJECTIVE

Conventional inferior alveolar nerve block (IANB) has a poor success rate in inflamed pulps. Three alternative techniques of providing anesthesia to mandibular molars were evaluated and compared with conventional IANB.

STUDY DESIGN

Ninety-seven adult volunteer subjects, actively experiencing pain, participated in this prospective, randomized, double-blinded study. Twenty-five patients received Gow-Gates mandibular conduction block anesthesia, 24 patients received "high" Vazirani-Akinosi inferior alveolar nerve block, 26 received only buccal-plus-lingual infiltrations, and 22 patients (control) received conventional IANB anesthesia. Endodontic access preparation was initiated after 15 minutes of anesthesia. Pain during treatment was recorded using a Heft-Parker visual analog scale. Success was recorded for "none" or "mild" pain.

RESULTS

Statistical analysis using nonparametric McNemer tests showed that Gow-Gates gave a success rate of 52%, which was statistically higher than control IANB (36%) (P < .05). Vazirani-Akinosi and infiltrations gave 41% and 27% success rates, respectively, with no statistically significant differences from control IANB.

CONCLUSIONS

Gow-Gates mandibular conduction anesthesia may increase the success rates in patients with irreversible pulpitis compared with conventional IANB. None of the techniques provided acceptable success rates.

Capsaicin-evoked iCGRP release from human dental pulp: a model system for the study of peripheral neuropeptide secretion in normal healthy tissue

The mechanisms underlying trigeminal pain conditions are incompletely understood. In vitro animal studies have elucidated various targets for pharmacological intervention; however, a lack of clinical models that allow evaluation of viable innervated human tissue has impeded successful translation of many preclinical findings into clinical therapeutics. Therefore, we developed and characterized an in vitro method that evaluates the responsiveness of isolated human nociceptors by measuring basal and stimulated release of neuropeptides from collected dental pulp biopsies. Informed consent was obtained from patients presenting for extraction of normal wisdom teeth. Patients were anesthetized using nerve block injection, teeth were extracted and bisected, and pulp was removed and superfused in vitro. Basal and capsaicin-evoked peripheral release of immunoreactive calcitonin gene-related peptide (iCGRP) was analyzed by enzyme immunoassay. The presence of nociceptive markers within neurons of the dental pulp was characterized using confocal microscopy. Capsaicin increased the release of iCGRP from dental pulp biopsies in a concentration-dependent manner. Stimulated release was dependent on extracellular calcium, reversed by a TRPV1 receptor antagonist, and desensitized acutely (tachyphylaxis) and pharmacologically by pretreatment with capsaicin. Superfusion with phorbol 12-myristate 13-acetate (PMA) increased basal and stimulated release, whereas PGE2 augmented only basal release. Compared with vehicle treatment, pretreatment with PGE2 induced competence for DAMGO to inhibit capsaicin-stimulated iCGRP release, similar to observations in animal models where inflammatory mediators induce competence for opioid inhibition. These results indicate that the release of iCGRP from human dental pulp provides a novel tool to determine the effects of pharmacological compounds on human nociceptor sensitivity.

Emerging peripheral receptor targets for deep-tissue craniofacial pain therapies

While effective therapies are available for some types of craniofacial pain, treatments for deep-tissue craniofacial pain such as temporomandibular disorders are less efficacious. Several ion channels and receptors which are prominent in craniofacial nociceptive mechanisms have been identified on trigeminal primary afferent neurons. Many of these receptors and channels exhibit unusual distributions compared with extracranial regions. For example, expression of the ATP receptor P2X(3) is strongly implicated in nociception and is more abundant on trigeminal primary afferent neurons than analogous extracranial neurons, making them potentially productive targets specifically for craniofacial pain therapies. The initial part of this review therefore focuses on P2X(3) as a potential therapeutic target to treat deep-tissue craniofacial pain. In the trigeminal ganglion, P2X(3) receptors are often co-expressed with the nociceptive neuropeptides CGRP and SP. Therefore, we discuss the role of CGRP and SP in deep-tissue craniofacial pain and suggest that neuropeptide antagonists, which have shown promise for the treatment of migraine, may have wider therapeutic potential, including the treatment of deep-tissue craniofacial pain. P2X(3), TRPV1, and ASIC3 are often co-expressed in trigeminal neurons, implying the formation of functional complexes that allow craniofacial nociceptive neurons to respond synergistically to altered ATP and pH in pain. Future therapeutics for craniofacial pain thus might be more efficacious if targeted at combinations of P2X(3), CGRP, TRPV1, and ASIC3.

Differential effect of extracellular acidosis on the release and dispersal of soluble and membrane proteins secreted from the Weibel-Palade body

Proteins secreted from Weibel-Palade bodies (WPBs) play important roles in regulating inflammatory and hemostatic responses. Inflammation is associated with the extracellular acidification of tissues and blood, conditions that can alter the behavior of secreted proteins. The effect of extracellular pH (pH(o)) on the release of von Willebrand factor (VWF), the VWF-propolypeptide (Proregion), interleukin-8, eotaxin-3, P-selectin, and CD63 from WPBs was investigated using biochemical approaches and by direct optical analysis of individual WPB fusion events in human endothelial cells expressing green or red fluorescent fusions of these different cargo proteins. Between pH(o) 7.4 and 7.0, ionomycin-evoked WPB exocytosis was characterized by the adhesion of VWF to the cell surface and the formation of long filamentous strands. The rapid dispersal of Proregion, interleukin-8, and eotaxin-3 into solution, and of P-selectin and CD63 into the plasma membrane, was unaltered over this pH(o) range. At pH(o) 6.8 or lower, Proregion remained associated with VWF, in many cases WPB failed to collapse fully and VWF failed to form filamentous strands. At pH(o) 6.5 dispersal of interleukin-8, eotaxin-3, and the membrane protein CD63 remained unaltered compared with that at pH(o) 7.4; however, P-selectin dispersal into the plasma membrane was significantly slowed. Thus, extracellular acidification to levels of pH(o) 6.8 or lower significantly alters the behavior of secreted VWF, Proregion, and P-selectin while rapid release of the small pro-inflammatory mediators IL-8 and eotaxin-3 is essentially unaltered. Together, these data suggest that WPB exocytosis during extracellular acidosis may favor the control of inflammatory processes.

Acid-sensitive ion channels and receptors

Acidosis is a noxious condition associated with inflammation, ischaemia or defective acid containment. As a consequence, acid sensing has evolved as an important property of afferent neurons with unmyelinated and thinly myelinated nerve fibres. Protons evoke multiple currents in primary afferent neurons, which are carried by several acid-sensitive ion channels. Among these, acid-sensing ion channels (ASICs) and transient receptor potential (TRP) vanilloid-1 (TRPV1) ion channels have been most thoroughly studied. ASICs survey moderate decreases in extracellular pH, whereas TRPV1 is activated only by severe acidosis resulting in pH values below 6. Two-pore-domain K(+) (K(2P)) channels are differentially regulated by small deviations of extra- or intracellular pH from physiological levels. Other acid-sensitive channels include TRPV4, TRPC4, TRPC5, TRPP2 (PKD2L1), ionotropic purinoceptors (P2X), inward rectifier K(+) channels, voltage-activated K(+) channels, L-type Ca(2+) channels, hyperpolarization-activated cyclic nucleotide gated channels, gap junction channels, and Cl(-) channels. In addition, acid-sensitive G protein coupled receptors have also been identified. Most of these molecular acid sensors are expressed by primary sensory neurons, although to different degrees and in various combinations. Emerging evidence indicates that many of the acid-sensitive ion channels and receptors play a role in acid sensing, acid-induced pain and acid-evoked feedback regulation of homeostatic reactions. The existence and apparent redundancy of multiple pH surveillance systems attests to the concept that acid-base regulation is a vital issue for cell and tissue homeostasis. Since upregulation and overactivity of acid sensors appear to contribute to various forms of chronic pain, acid-sensitive ion channels and receptors are considered as targets for novel analgesic drugs. This approach will only be successful if the pathological implications of acid sensors can be differentiated pharmacologically from their physiological function.

Injection of adjuvant but not acidic saline into craniofacial muscle evokes nociceptive behaviors and neuropeptide expression

Craniofacial muscle pain including muscular temporomandibular disorders accounts for a substantial portion of all pain perceived in the head and neck region. In spite of its high clinical prevalence, the mechanisms of chronic craniofacial muscle pain are not well understood. Injection of acidic saline into rodent hindlimb muscles produces pathologies which resemble muscular pathologies in chronic pain patients. Here we investigated whether analogous transformations occur following repeated injections of acidic saline into the rat masseter muscle. Injection of acidic saline (pH 4) into the masseter muscle transiently lowered i.m. pH to levels comparable to those reported for rodent hindlimb muscles. Nevertheless, repeated unilateral or bilateral injections of acidic saline (pH 4) into the masseter muscle failed to alter nociceptive behavioral responses as occurs in the hindlimb. Changing the pH of injected saline to pH 3.0 or 5.0 also did not evoke nocifensive behavior. Acid sensing ion channel 3 receptors, which are implicated in transformations following acidification of hindlimb muscles, were found on trigeminal ganglion muscle afferent neurons via combined neuronal tracing and immunocytochemistry. In contrast to the acidic saline, injection of complete Freund's adjuvant (CFA) into the masseter muscle induced mechanical allodynia for 3 weeks, thermal hyperalgesia for 1 week and an increase in the number of calcitonin gene-related peptide (CGRP)-immunoreactive muscle afferent neurons in the trigeminal ganglion. Although pH may alter CGRP release in primary afferent neurons, the number of CGRP-muscle afferent neurons did not change following i.m. injection of acidic saline. Further, there was no change in ganglionic iCGRP levels at 1, 4 or 12 days after i.m. injection of acidic saline. While these findings extend our earlier reports that CFA-induced muscle inflammation results in behavioral and neuropeptide changes they further suggest that i.m. acidification in craniofacial muscle evokes different responses than in hindlimb muscle and imply that disparate proton sensing mechanisms underlie these discrepancies.